Generally speaking, there are two types of RF signal coupling between uhf rfid reader and electronic tag.

(1) Inductive coupling, that is, the transformer model uses high-frequency alternating magnetic fields in space to achieve coupling, based on the law of electromagnetic induction.

(2) Electromagnetic backscatter coupling: Generally, this is based on the radar principle model. The electromagnetic waves emitted are reflected by the target and carried back to the target information. The basis here is the spatial propagation law of electromagnetic waves.

In frequency, the inductive coupling method is generally suitable for short-range radio frequency identification systems that operate at medium and low frequencies. Typical operating frequencies are: 125kHz, 225kHz and 13.56MHz. The identification action distance is less than 1m, and the typical action distance is 10-20cra.

The electromagnetic backscatter coupling method is a long-range radio frequency identification system generally suitable for high-frequency and microwave operation. Typical operating frequencies are: 433MHz, 915MHz, 2.45GHz, 5.8GHz. The identification action distance is greater than 1m, and the typical action distance is 3-10m.